1. Field of the Disclosure
This disclosure relates to a liquid crystal display device with a touch sense element, and particularly a liquid crystal display (LCD) device improving the perception ratio and accuracy of the sense element.
2. Description of the Related Art
Recently, a display field regarding the visual display of electric information signals is being developed as the substantial starting of an information age. In accordance therewith, various flat display devices with superior features such as thin profile, light weight, low power consumption, and similar features have been developed and rapidly (increasingly) replaced the previous cathode ray tube (or the Brown-tube).
Actually, these flat display devices include an LCD device, a plasma display panel (PDP) device, a field emission display (FED) device, and an electro luminescence (ELD) device, and so on. Also, these flat display devices commonly have a flat display panel, which consists of a pair of transparent isolation substrates bonded in opposition to each other at the center of a light emitting or polarizing material in order to screen pictures, as an indispensable factor (or element).
Among the flat display devices, the LCD device uses an electric field and controls the light transmissivity of the liquid crystal, thereby displaying a picture. To this end, the LCD device is configured to include a display panel with liquid crystal cells, a backlight unit irradiating lights to the display panel, and a drive circuit driving the backlight unit and the liquid crystal cells.
The display panel is configured to define a plurality of unit pixel regions by means of a plurality of gate lines and a plurality of data lines intersecting each other. More specifically, the display panel includes a thin film transistor array substrate and a color filter array substrate in opposition to each other, spaces positioned to maintain a constant cell gab between the substrates, and a liquid crystal filled in the cell gab.
The thin film transistor array substrate has a combination of the gate lines and the data lines, a thin film transistor formed in every intersection region of the gate line and the data line, pixel electrodes formed in the liquid crystal cell unit and connected to the thin film transistors, respectively, and an alignment film coated on the pixel electrodes. The gate lines and the data lines receive signals from the drive circuits through respective pad portions. The thin film transistors respond to scan signals on the gate lines and apply pixel voltage signals on the respective data lines to the respective pixel electrodes.
The color filter array substrate consists of color filters formed in a liquid crystal cell unit, a black matrix for defining the color filters and shielding lights from the exterior, and an alignment film coated on the filters and the black matrix.
These thin film transistor array substrate and color filter array substrate separately manufactured as described above, are completed through processes of a facing arrangement, a bonding, an injection of liquid crystal, and a sealing.
In such an LCD device including the aforementioned display panel, there have been attempts to form a light sensor inside the display panel in order to control the backlight unit in accordance with the brightness of an external light. Moreover, it has attempted to form a touch panel inside the display panel so as to reduce the size of the LCD device which had been enlarged by attaching the touch panel to the external of the display panel.
FIG. 1 is a circuit diagram showing a sense unit included in a related art LCD device, and FIG. 2 is a waveform diagram showing the waveforms of signals applied to the related art LCD device
Referring to FIGS. 1 and 2, the sense unit loaded on the related art LCD device includes a sense element Tph sensing a touch with a liquid crystal panel, a sensor drive voltage line applying a drive voltage Vsto to the sense element Tph, a sensor bias voltage line applying a bias voltage Vbias to the sense element Tph, a capacitor Cst storing a signal sensed by the sense element Tph, a thin film transistor Tsw responding to a scan pulse (or a gate pulse) on a preceding gate line GLn−1 to output the sensed signal stored in the capacitor Cst, and a read-out line ROline applying the sensed signal from the thin film transistor Tsw to a sense processor (not shown).
The related art sense unit of the aforementioned configuration outputs the sensed signal stored in the capacitor Cst via the read-out line ROline, when a scan signal is applied to the preceding gate line GLn−1 during the interval which pixel voltage signals are applied to the data lines DL by a source output enable signal SOE changed into a second level voltage (or a low logic level). The pixel voltage signals and the sensed signal are affected by a parasitic capacitance existed between the read-out line ROline and the data line DL. Therefore, the sensed signal should include cross talk and noise.
Moreover, since the pixel voltage signals applied to the data lines DL have different levels from each other, the cross-talk and noise included in the sensed signal, which is being affected by the pixel voltage signal, should increase. As a result, the perception ratio and accuracy of the sense element are deteriorated.